1. Technical Field
The disclosure relates in general to a semiconductor structure, and more particularly to a semiconductor structure designed for memory device with bit lines and ground lines.
2. Description of the Related Art
In typical MOSFET (metal-oxide-semiconductor field-effect transistor), the bulk end (body or substrate) and the source end have the same electric potential, and the voltage of source-body junction is zero.
However, the bulk end and the source end may not connect directly in some circuit design. In this situation, the extra loading in circuit may generate bias at source end (VS), resulting in changes in threshold voltage (VT). This phenomenon is called body effect.
When a plurality of transistors are connected in series (such as the bit lines in memory device), the body effect may significantly change the VT of transistor, influences the character of circuit. Thus, it is necessary to diminish the body effect. The traditional flash memory will introduce huge metal ground lines for diminishing the body effect. Nevertheless, the huge metal ground lines in prior art not only take the effective area of circuit, but also influence the nearby bit line. The electrical character of bit lines being adjacent to the ground lines will be changed by loading effect and coupling effect of surrounding circuit. Therefore, bit lines being adjacent to the ground lines have to be designed as dummy line, which increases the manufacturing cost.